assume cs:codesg

codesg segment

        mov ax,4c00h
        int 21h

start:  mov ax,0

s:      nop
        nop

        mov di,offset s
        mov si,offset s2
        mov ax,cs:[si]
        mov cs:[di],ax

s0:     jmp short s

s1:     mov ax,0
        int 21h
        mov ax,0

s2:     jmp short s1
        nop

codesg ends

end start

